DENTAL WEDGE
A dental wedge for inserting into the interproximal space between adjacent teeth comprises a first and second sidewall comprised of a shape memory material, including a nickel-titanium alloy, wherein the dental wedge is in a first, resting state when outside of the interproximal space and transforms to a second, operational state when the dental wedge is interested into the interproximal space between adjacent teeth and exposed to a first transformation stimulus, namely exposure to the higher temperature in the interproximal space. The expansion force generated by the dental wedge when in the second, operational stage is sufficient to secure a dental matrix against the tooth being restored and to separate the tooth being restored and adjacent tooth to expand the interproximal space.
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This application claims the benefit of New Zealand Provisional Specification Serial No. 618394, filed Nov. 29, 2013, the contents of which are incorporated by reference herein.
FIELD OF THE INVENTIONThe present invention relates to dental wedges for use during direct restoration of teeth having damaged portion or dental carries requiring restoration.
BACKGROUND OF THE INVENTIONDirect dental restorations typically involves the use of devices to separate the tooth being restored from the adjacent tooth to increase the interproximal space between the teeth and to secure a dental matrix against the tooth being restored to prevent undesirable flow of the dental restoration material from the restoration area. The mechanical expansion force required to accomplish these tasks is typically provided by a matrix retainer clip and supplemented by a dental wedge to secure the matrix to the tooth at the gingival margin. However, the interproximal space between the teeth is small and may not have uniform, convenient dimensions rendering the use of multiple devices in a crowded space more cumbersome that necessary for dental professionals to quickly and accurately restore teeth.
SUMMARY OF THE INVENTIONThe present invention is a dental wedge with the benefit of enabling a dentist to more easily separate adjacent teeth during a restorative procedure and support a dental matrix band for the same purpose. The dental inserts into the interproximal space between a first tooth being restored and a second, adjacent tooth and comprises a first sidewall comprising an internal portion and configured to engage the first tooth; a second sidewall comprising an internal portion and configured to engage the second tooth; and a bridge disposed between and connecting the first sidewall and second sidewall to form an inverted V-shaped cross section throughout the internal portions of the first sidewall and second sidewall. The first sidewall and second sidewall consisting essentially of a shape memory material enabling the first sidewall and second sidewall to transform from a first, resting state wherein the dental wedge is readily deformable to a second, operational state wherein the dental wedge returns to a preformed shape and exerts an expansion force on the first tooth being restored and the second, adjacent tooth. The shape memory material comprises a shape memory alloy, and is preferably a nickel-titanium alloy. The shape memory material can also be a shape memory polymer.
Each of the first and second sidewalls 22, 24 comprises a top edge 28a, b, bottom edge 30a, b, and opposing side edges 32a, b, 34a, b, and interior 36a, b and exterior 38a, b surfaces. The top edges 28a, b shown in
The first and second sidewalls 22, 24 further comprises an interior portion 40a, b and first and second wings 42a, b, 44a, b extending from opposing sides of the interior portions 40a, b of the first and second sidewalls 22, 24. As seen in
The first and second sidewalls 22, 24 and bridge 26 of the dental wedge 10 are comprised of a shape memory material that enables the dental wedge 10 to transform from a first, resting state to a second, operational state in the presence of and in response to a first transformation stimulus. The use of the shape memory material also enables the dental wedge 10 to transform from the second state back to the first stage when the first transformation stimulus is removed or in the presence of a second transformation stimulus. The shape memory material may be a shape memory alloy or shape memory polymer that are biocompatible and exhibit suitable shape memory and superelastic properties. The dental wedge 10 manufactured from such a shape memory material will be inserted into the interproximal space between the tooth being restored and adjacent tooth when the dental wedge is in its first, resting state and will transform the second, operational state in response to a first transformation stimulus, namely, the increased temperature in the patient's mouth. The transformation activates a compressive force that is sufficient to both separate the adjacent teeth and secure a dental matrix against the tooth being restored. The expansion force is continuously applied as long as the dental matrix remains in the second state. Removing the dental wedge 10 from the patient's mouth, thereby removing the first transformation stimulus, enables the dental wedge to 10 return to its first, resting state. Exposing the dental wedge 10 to a second transformation stimulus, such as the cool environment of a refrigerator or a coolant spray also enables the dental wedge 10 to return to the first, resting state.
Shape memory alloys suitable for the making the dental wedge 10 of the present invention include alloys composed substantially of nickel and titanium (NiTi) or alloys of other metals known to exhibit shape memory effects, such as CuZnAl, CuAlNi, FeNiAl, and InTi. Elements such as boron, cerium, cobalt, iron, copper, vanadium, and zirconium may also be added to tailor the mechanical properties to the intended application. One exemplary shape memory alloy is nitinol (NiTi). NiTi undergoes a phase transformation in its crystal structure when heated from its weaker, low temperature phase (Martensite) to its stronger, high temperature phase (Austenite) and from Austentite to Martensite during a cooling process. In the Martensitic phase, the NiTi is readily workable and malleable and the dental wedge 10 may be manipulated into a configuration rendering it easier for the dental professional to insert the wedge 10 into the interproximal space between the tooth being restored and the adjacent tooth. As shown in
Useful shape memory polymers include segmented linear polyurethanes having hard segments and a soft segments. The hard segments are typically crystalline, with a defined melting point, and the soft segments are typically amorphous, with a defined glass transition temperature. Suitable polymers used to prepare the hard and soft segments include various polyethers, polyacrylates, polyamides, polysiloxanes, polyurethanes, polyether amides, polyurethane/ureas, polyether esters, urethane/butadiene copolymers, and polyesters. Examples of shape memory polymers are described in U.S. Pat. No. 6,169,084 to Langer et al., U.S. Pat. No. 5,145,935 to Hayashi et al., U.S. Pat. No. 5,665,822 to Bitler et al., and U.S. Pat. No. 5,506,300 to Ward et al.
The dental wedge 10 of the present invention made from a shape memory alloy, such as NiTi metal alloy, is shaped into the form seen in appended figures by a series of steps involving bending, twisting, or squeezing of a sheet of the raw material, and made to retain its new shape using a combination of mechanical and thermal “training” or “setting” steps. The training/setting process generally involves heating the formed configuration to a suitable heat treatment temperature and quickly cooling it in a water bath or by rapid air cooling, thus freezing the NiTi's crystalline structure in a new position.
The dental wedge 10 may be formed from a sheet of NiTi material with a thickness of approximately 0.1-0.5 mm. The basic, two-dimensional shape of the wedge can be stamped, cut, laser or chemical etched from the sheet of raw material and then shaped into its desired form. The height of the sidewalls 22, 24 is approximately 3-4 mm and the angle A of the sidewalls is approximately 30 deg. The width of the bridge 26 may vary for use in interproximal spaces of different dimension. If the interproximal space is wide it will be desirable to have a wider bridge 26 to avoid a requirement for taller sidewalls 22, 24. The overall length of each sidewall 42, 44 is selected based on the intended application of the dental wedge 10 and the length of the bridge 26, and corresponding length of the wings 42a, b and 44a, b is selected also based on the desired wrap around on the first and second teeth. Once in the desired shape the dental wedge will undergo the “training” or “setting” steps to retain the final form of the wedge.
A combination of heat-treating and cold working with control the final properties of the NiTi. Specifically, Austenite start temperature AS and finish temperature AF are preferably within a range encountered outside of the patient's mouth where the ambient temperature will be less than the temperature in the interproximal space between the first and second teeth. This enables the wedge to transform from its weaker, low temperature Martensite state to the stronger, higher temperature Austenite state while the dental professional is placing the dental wedge 10. The AS-AF range must be formed while enabling the wedge to generate and apply a suitable expansion force on the tooth being restored and adjacent tooth to separate the teeth at least 30 microns and preferably between 50-100 microns and for the expansion force to be consistently applied over a timeframe of 5-10 minutes with the restoration is completed.
Likewise, the Martensite start temperature MS and finish temperature MF range must occur at the typical ambient room temperature less than the temperature present in the interproximal space between the first and second teeth or across a range of cooling temperatures readily attainable by refrigeration, freezing or exposure to a coolant spray. Preferably, the wedge shape cut from the NiTi sheet is cooled to below its AS temperature and then formed into its final configuration seen in
The dental wedge 10 may also be manufactured by a variety of conventional polymer processing techniques, including, for example, extrusion, injection molding, liquid injection molding, compression molding, reaction injection molding, pressing, drawing, and die cutting.
In operation after the dental carry or damaged portion 20 is removed and the restoration area 18 is prepared, the dental wedge 10 in its shape memory form (
As seen in
While the present invention has been described in connection with a specific application, this application is exemplary in nature and is not intended to be limiting on the possible applications of this invention. It will be understood that modifications and variations may be effected without departing from the spirit and scope of the present invention. It will be appreciated that the present disclosure is intended as an exemplification of the invention and is not intended to limit the invention to the specific embodiments illustrated and described. The disclosure is intended to cover, by the appended claims, all such modifications as fall within the scope of the claims.
Claims
1. A dental wedge to insert into the interproximal space between a first tooth being restored and a second, adjacent tooth, the dental wedge comprising:
- a first sidewall comprising an internal portion and configured to engage the first tooth;
- a second sidewall comprising an internal portion and configured to engage the second tooth;
- a bridge disposed between and connecting the first sidewall and second sidewall to form an inverted V-shaped cross section throughout the internal portions of the first sidewall and second sidewall;
- the first sidewall and second sidewall consisting essentially of a shape memory material enabling the first sidewall and second sidewall to transform from a first, resting state wherein the dental wedge is readily deformable to a second, operational state wherein the dental wedge returns to the inverted V-shaped cross section throughout the length of the internal portions of the first and second sidewalls and exerts an expansion force on the first tooth being restored and the second, adjacent tooth.
2. The dental wedge of claim 1 wherein the shape memory material comprises a shape memory alloy.
3. The dental wedge of claim 2 wherein the shape member alloy is a nickel-titanium alloy.
4. The dental wedge of claim 3 wherein the nickel-titanium alloy is in a Martensite phase when the dental wedge is in its first, resting state and wherein the nickel-titanium ally is in an Austenite phase when the dental wedge is in the second, operational state.
5. The dental wedge of claim 4 wherein the transformation from the Martensite phase to the Austenite state occurs in response to the first transformation stimulus and the first transformation stimulus comprises a first ambient temperature less than a first interproximal space temperature present in the interproximal space between the first and the second tooth.
6. The dental wedge of claim 4 wherein the transformation from the Austenite state to the Martensite state occurs in response to a second transformation stimulus comprising a second ambient temperature less than a first interproximal space temperature present in the interproximal space between the first and the second tooth.
7. The dental wedge of claim 1 wherein the bridge comprises substantially planar member with a length and a width wherein the length is greater than the width.
8. The dental wedge of claim 1 wherein the dental wedge is formed from a single piece of shape memory material and the first sidewall, second sidewall, and bridge are integrally formed.
9. The dental wedge of claim 1 wherein the expansion force is sufficient to separate the first tooth being restored and the second, adjacent tooth.
10. The dental wedge of claim 9 wherein the expansion force is sufficient to separate the first and second tooth at least 30 microns.
11. The dental wedge of claim 9 wherein the expansion force is sufficient to separate the first and second tooth by 50-100 microns.
12. The dental wedge of claim 1 wherein the expansion force is sufficient to secure the dental matrix against the first tooth.
13. The dental wedge of claim 1 wherein the dental wedge in the second, operational stage exerts the expansion force at a consistent rate over a first time period of 5-10 minutes.
14. The dental wedge of claim 1 wherein the first and second sidewalls in the V-shape configuration are space apart approximately 30 degrees in the second, operational state.
15. The dental wedge of claim 1 wherein the first and second sidewalls in the V-shape configuration can be deformed to be spaced apart by approximately 10-15 degrees.
16. The dental wedge of claim 4 wherein the Austenite phase has a start temperature AS and a finish temperature AF and the AF temperature is less than a first interproximal space temperature present in the interproximal space between the first and the second tooth.
17. The dental wedge of claim 4 wherein the Martensite phase has a start temperature MS and a finish temperature MF and the MS temperature is less than a first interproximal space temperature present in the interproximal space between the first and the second tooth.
18. The dental wedge of claim 1 wherein the first and second sidewalls each further comprise a first and second wing extending from the interior portion of the first and second sidewalls, the first wings of each of the first and second sidewalls and the second wings of each of the first and second sidewalls curving away from each other when the dental wedge is in the second, operational state.
19. The dental wedge of claim 1 wherein the shape memory material comprises a shape memory polymer.
20. A dental wedge to insert into the interproximal space between a first tooth being restored and a second, adjacent tooth, the dental wedge comprising:
- a first sidewall comprising an internal portion with a length and a first and second wing extending from the internal portion, the first sidewall configured to engage the first tooth;
- a second sidewall comprising an internal portion with a length and a first and second wing extending from the internal portion, the second sidewall configured to engage the second tooth;
- a bridge disposed between and connecting the first sidewall and second sidewall to form an inverted V-shaped cross section throughout the length of the internal portions of the first sidewall and second sidewall and the first wings of each of the first and second sidewalls and the second wings of each of the first and second sidewalls curve away from each other;
- the first sidewall and second sidewall consisting essentially of a shape memory material enabling the first sidewall and second sidewall to transform from a first, resting state wherein the dental wedge is readily deformable to a second, operational state wherein the dental wedge returns to the inverted V-shaped cross section throughout the length of the internal portions of the first and second sidewalls and exerts an expansion force on the first tooth being restored and the second, adjacent tooth.
21. The dental wedge of claim 20 wherein the shape memory material comprises a shape memory alloy.
22. The dental wedge of claim 21 wherein the shape member alloy is a nickel-titanium alloy.
23. The dental wedge of claim 22 wherein the nickel-titanium alloy is in a Martensite phase when the dental wedge is in its first, resting state and wherein the nickel-titanium ally is in an Austenite phase when the dental wedge is in the second, operational state wherein the Martensite phase has a start temperature MS and a finish temperature MF and the MS temperature is less than a first interproximal space temperature present in the interproximal space between the first and the second tooth and wherein the Austenite phase has a start temperature AS and a finish temperature AF and the AF temperature is less than a first interproximal space temperature present in the interproximal space between the first and the second tooth.
24. The dental wedge of claim 20 wherein the expansion force is sufficient to secure the dental matrix against the first tooth and is sufficient to separate the first tooth being restored and the second, adjacent tooth.
25. The dental wedge of claim 20 wherein the shape memory material comprises a shape memory polymer.
26. A dental wedge to insert into the interproximal space between a first tooth being restored and a second, adjacent tooth, the dental wedge comprising a first and second opposing sidewall formed into an inverted V-shape through at least a first portion of a length of the first and second sidewalls, the first and second sidewalls composed of a shape memory material and transformable from a first state wherein the first and second sidewalls are readily deformable to a second state wherein the first and second sidewalls return to the inverted V-shape throughout at least the first portion of the length of the first and sidewalls and the first and second sidewalls exert an expansion force on the first and second teeth.
27. The dental wedge of claim 26 wherein the shape memory material comprises a shape memory alloy.
28. The dental wedge of claim 27 wherein the shape member alloy is a nickel-titanium alloy.
29. The dental wedge of claim 28 wherein the nickel-titanium alloy is in a Martensite phase when the dental wedge is in its first, resting state and wherein the nickel-titanium ally is in an Austenite phase when the dental wedge is in the second, operational state wherein the Martensite phase has a start temperature MS and a finish temperature MF and the MS temperature is less than a first interproximal space temperature present in the interproximal space between the first and the second tooth and wherein the Austenite phase has a start temperature AS and a finish temperature AF and the AF temperature is less than a first interproximal space temperature present in the interproximal space between the first and the second tooth.
30. The dental wedge of claim 26 wherein the shape memory material comprises a shape memory polymer.
Type: Application
Filed: Nov 28, 2014
Publication Date: Jun 4, 2015
Patent Grant number: 9883922
Applicant: DENTSPLY International Inc. (York, PA)
Inventor: Simon Paul MCDONALD (Katikati)
Application Number: 14/556,092